Hhhhmmm...probably, yes. So long as they keep it to under $5/month.
But I would prefer if they just sold single player games separately from multiplayer games. So I could purchase the Killzone 3 single plalyer/local co-op for $25, then if I choose I would pay $35 for the multiplayer..which would have the online costs built-in. Or something like that.
I like to play single player for pretty much every game, but only have time to play multiplayer for like 4 games throughout the year...yet I pay for both when I purchase the game for $60.